As has been well known, ultraviolet rays in the sunlight degrades polymers by breaking the chemical bonds in the polymers. In order to prevent such degradation, light stabilizers, ultraviolet absorbers, or the like are added to polymer products such as plastics, fibers, and paints. In particular, a hindered amine light stabilizer (hereinafter referred to as HALS) is said to have a function of preventing a polymer material from being degraded because the HALS hardly absorb the ultraviolet ray while efficiently scavenging harmful free radicals generated by ultraviolet rays.
A typical HALS, however, is not chemically bonded to a polymer material. Thus, the HALS may bleed out from the polymer material if exposed outdoors for a long time. Therefore, it has been pointed out that such bleeding out of the HALS may lead to the loss of the original functions of the HALS. For suppressing the bleeding out of the HALS from the polymer material, a high molecular weight HALS prepared from methacrylic acid piperidyl ester has been studied (see, Patent Documents 1 to 3).